如何将两个 System.Io.Stream 实例连接成一个?

问题描述

让我们假设我想连续将三个文件流式传输给一个用户，但不是他递给我一个 Stream 对象来向下推字节，我必须递给他一个 Stream 对象，他将从中提取字节.我想使用我的三个 FileStream 对象(或者更聪明的 IEnumerable)并返回一个新的 ConcatenatedStream 对象按需从源流中提取.

Let's imagine I want to stream three files to a user all in a row, but instead of him handing me a Stream object to push bytes down, I have to hand him a Stream object he'll pull bytes from. I'd like to take my three FileStream objects (or even cleverer, an IEnumerable<Stream>) and return a new ConcatenatedStream object that would pull from the source streams on demand.

推荐答案

class ConcatenatedStream : Stream
{
    Queue<Stream> streams;

    public ConcatenatedStream(IEnumerable<Stream> streams)
    {
        this.streams = new Queue<Stream>(streams);
    }

    public override bool CanRead
    {
        get { return true; }
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        int totalBytesRead = 0;

        while (count > 0 && streams.Count > 0)
        {
            int bytesRead = streams.Peek().Read(buffer, offset, count);
            if (bytesRead == 0)
            {
                streams.Dequeue().Dispose();
                continue;
            }

            totalBytesRead += bytesRead;
            offset += bytesRead;
            count -= bytesRead;
        }

        return totalBytesRead;
    }

    public override bool CanSeek
    {
        get { return false; }
    }

    public override bool CanWrite
    {
        get { return false; }
    }

    public override void Flush()
    {
        throw new NotImplementedException();
    }

    public override long Length
    {
        get { throw new NotImplementedException(); }
    }

    public override long Position
    {
        get
        {
            throw new NotImplementedException();
        }
        set
        {
            throw new NotImplementedException();
        }
    }

    public override long Seek(long offset, SeekOrigin origin)
    {
        throw new NotImplementedException();
    }

    public override void SetLength(long value)
    {
        throw new NotImplementedException();
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        throw new NotImplementedException();
    }
}